This invention pertains to an apparatus and method for packaging articles, and more specifically to packaging of articles in heat sealable barrier films.
In packaging articles, and especially food articles such as blocks of cheese, the horizontal form-fill-seal machine has been used for many years and proven to be a useful and economic way of continuously packaging such articles.
This arrangement generally involves the continuous feeding of rollstock film or laminate onto a horizontal surface, and the infeeding of discrete articles at spaced intervals onto the film, followed by forming a tube of the film around the articles in a continuous fashion. The articles, for example, food items such as cheese blocks and the like, are drawn within the tube onto a wheel or turret where sealing dies grasp the tube at intervals between the articles and draw each packaged article around the wheel, effecting a transverse seal and a subsequent severing of the tube in the seal area to produce discrete packages which are typically dropped to a conveyor for further processing or packaging.
Prior to the passage of the enclosed article onto the wheel or turret, a longitudinal sealer effects a thin seal on the tube to produce a longitudinal seal in a continuous manner.
Exemplary of this technology is U.S. Pat. No. 2,976,657 (Cloud) which generally describes the process and apparatus, and in particular the wheel or turret means which carries the sealing dies for transverse sealing of the tube. This reference discloses various means for end sealing and severing the packages on the wheel, including brief heating of the heat sealer and clamping at cooler temperatures to hold the material until the heat seal has cooled. Coordination means for coordinating the feeding of film, articles to be packaged, and operation of the wheel or turret is also discussed.
Another reference, U.S. Pat. No. 3,024,581 (Cloud) discusses a similar apparatus in which tube forming guides are used to curl the sides of the film and use the loops at the film sides to support them and draw them up and over the objects to be packaged.
Also of interest is U.S. Pat. No. 3,126,682 (Krance) disclosing the use of a similar arrangement for forming a tube of heat shrinkable film about a candle or other article to be wrapped, and sequentially grasping the tube at intervals between the packaged articles, and heating the tube to permit shrinkage of the film about the article, thereafter severing each wrapped article.
U.S. Pat. No. 3,274,746 (James et al) discloses the packaging of cheese in a horizontal form-fill-seal arrangement and using gas flushing to monitor and control the internal atmosphere of the package.
U.S. Pat. No. 3,942,304 (Hart et al) discloses an improvement in the coupling/uncoupling means disclosed in U.S. Pat. No. 2,976,657 (Cloud) comprising a coupling/uncoupling means located on both sides of the wheel or turret.
U.S. Pat. No. 3,943,683 (Kovacs et al) discloses the use of an electronic pulse counter, also related to an improvement on U.S. Pat. No. 2,976,657 to Cloud.
Still another improvement in horizontal form-fill-seal technology is U.S. Pat. No. 3,958,390 (Pringle et al) which describes improvements on U.S. Pat. No. 3,274,746 to James et al, and more specifically the use of hot gas to effect the longitudinal seal.
Yet another improvement in means for limiting angular movement of the sealing units in the wheel or turret area of horizontal form-fill-seal equipment is disclosed in U.S. Pat. No. 3,992,851 (James et al) describing a plurality of contact pads carried by portions of each sealing unit on each side of a circular member for sliding engagement therewith.
As discussed earlier, the general horizontal form-fill-seal arrangement, using the simultaneous infeeding of thermoplastic film or laminate and articles placed on the film at spaced intervals, longitudinally sealing the film or laminate to form a tube and transversely sealing the film at intervals between packaged articles, has been a generally successful means for packaging articles such as food products, including blocks of cheese. Exemplary of such an apparatus is the Hayssen RT-118 horizontal form-fill-seal machine.
It would be desirable to use such equipment in connection with certain kinds of oxygen barrier film in order to increase the package shelflife and to permit a shrinkable film to be used which will result in a tighter, more esthetic finished package. It would also be advantageous to utilize a shrink barrier film that can provide a homogeneous/hermetic seal that can be easily inspected.
Unfortunately, the seal bars currently installed on such equipment are typically thermal bars which are continuously heated causing the shrink barrier films to shrink, and resulting in capillaries and voids in the seal area. This can reduce the esthetic appearance of the package and in some cases effect the hermetic seal, resulting in lost product.
Another disadvantage of the currently available equipment is the inability of the film tracking portion of this equipment to adequately support these same shrink barrier films prior to longitudinal sealing. This disadvantage arises from the relatively thin gauge of the shrink barrier films compared with relatively thick conventional laminates. These thinner films lack the vertical support inherent in thicker laminates.
It is therefore an object of the present invention to provide a seal arrangement for the transverse sealing function of such horizontal form-fill-seal equipment in order to permit the use of shrink barrier films having the characteristics described above.
It is an additional object of the present invention to provide film tracking means for supporting such shrink barrier films prior to longitudinally sealing the film.